The treatment of many medical conditions requires the subcutaneous delivery of a medicament. As one example, the treatment of diabetes requires the subcutaneous delivery of insulin. In some instances, subcutaneously delivered medicament must be continuously delivered in small and at time varying doses over a long period of time. It is important that such delivery be accurate, as over or under delivery can cause serious health risks. For example, the subcutaneous delivery of insulin can require accuracies as low as 0.5 microliters per hour. One widely used technique for subcutaneously delivering medicament is by pumping the medicament from a large external storage container through a long tube to a cannula of an infusion set attached to a patient's skin. An improvement over this technique is the use of a patch pump. A patch pump incorporates the medicament, pumping mechanism, and infusion set into a patch that attaches to a patient's skin, thus eliminating the need for long tubes. However, existing patch pumps still present a number of drawbacks and their overall adoption is low compared to the use of syringes and syringe pens. Such pumps are rigid and bulky and consequently are prone to detachment and/or require the use of aggressive adhesives to adhere to the skin, which can lead to irritation. Further, because existing pumps usually contain a single reservoir or at most two (e.g. reservoirs for insulin and potentially glucagon), they are also limited in their ability to deliver combination therapies, requiring patients to use separate patch pumps to deliver multiple medicaments. In addition, the use of a single or dual reservoir(s) can make it difficult to control the delivery of accurate amounts of medicament. Some prior art pumps require a flow meter to determine the amount of medicament delivered, which can lead to imprecise measurements.
Accordingly, there exists a need for an improved patch pump.